In existing signal transmission technologies, different time intervals are normally adopted to distinguish different bit values from each other. For example, bit 00 is represented by T+t1, bit 01 is represented by T+t2, bit 10 is represented by T+t3 and bit 11 is represented by T+t4. With the existing signal transmission technologies, the time required to transmit different bit values is long, the coding efficiency for data bits is low and burdens as well as costs on sending and receiving terminals are raised.
In addition, in the prior art, in a data transmission process, usually only when the sending terminal finishes sending all the data packets will it receive a retransmission request from the receiving terminal, the sending terminal will then retransmit all the data or the data packets that the receiving terminal fails to receive, both of which will cause a lowered data retransmission efficiency and an increased data transmission amount.